Thanks for your replyes guys. I also seen, companys are using ready made black box so called PLC, becoz they dont have time to wait for the control system using 8051. Since any one who have a basic knowledg of electrical/electronics can programe the PLC. One thing is clear, I have noticed for last one year that there is more jobs for PLC programmer then 8051. This is a situation here in Bombay.

Bye